Digital images may be represented in a grid arrangement, where each position within the grid is called a pixel. A color image pixel may be represented by numeric Red, Green, Blue (RGB) values that correspond to a particular color. There are several different binary digital representations of RGB values, but the main characteristic of all of them is representing the values as integer numbers within some range, usually from 0 to a number equivalent to a power of two minus one (e.g., 2n−1) in order to fit them into bit groupings. The values may be represented in either decimal or hexadecimal notation. For example, RGB values encoded in 24 bits-per-pixel may be specified using three 8-bit unsigned integers (0 through 255) representing intensities of red, green and blue. The composite of the three eight bit numbers is the final representation associated to each pixel and defines the color of the pixel. For example, a black pixel has the composite value of (0, 0, 0), meaning red=0, green=0, blue=0. A white pixel has the composite value of (255, 255, 255). A yellow pixel has the composite value of (255, 255, 0).
The colors of pixels in an image may be defined using color space representations other than RGB, such as Hue, Saturation and Lightness (HSL) or Hue, Saturation and Value (HSV). Hue is one of the three main attributes of perceived color, in addition to lightness and chroma (i.e., colorfulness). Usually, colors with the same hue are distinguished with adjectives referring to their lightness and/or chroma, such as “light blue”, “pastel blue”, “vivid blue”. Exceptions include brown, which is a dark orange, and pink, which is a light red with reduced chroma. Saturation is the colorfulness of a stimulus relative to its own brightness. A highly colorful stimulus is vivid and intense, while a less colorful stimulus appears more muted, closer to gray. With the three attributes—colorfulness (e.g., chroma or saturation), lightness (or brightness), and hue—any color can be described.
Image-editing is the process of altering, manipulating, enhancing and transforming digital images. Image-editing software may be broadly grouped into vector graphics editors, raster graphics editors and 3d modelers. Image-editing programs may be used to render or create digital images.
Image-editing applications, such as Adobe Photoshop™, may change the pixel information in order to enhance the image. Pixels may be changed as a group or individually by transformation operations executed by the image-editing application.